Abalone are marine snails. Their taxonomy puts them in the family Haliotidae which contains only one genus, Haliotis, which once contained six subgenera. These subgenera have become alternate representations of Haliotis.[4] The number of species recognized worldwide ranges between 30[6] and 130[7] with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies.[8]

The shells of abalones have a low, open spiral structure, and are characterized by several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre (mother-of-pearl), which in many species is highly iridescent, giving rise to a range of strong, changeable colors, which make the shells attractive to humans as decorative objects, jewelry, and as a source of colorful mother-of-pearl.

The flesh of abalones is widely considered to be a desirable food, and is consumed raw or cooked by a variety of cultures.

The shell of abalones is convex, rounded to oval in shape, and may be highly arched or very flattened. The shell of the majority of species has a small, flat spire and two to three whorls. The last whorl, known as the body whorl, is auriform, meaning that the shell resembles an ear, giving rise to the common name "ear shell". Haliotis asinina has a somewhat different shape, as it is more elongated and distended. The shell of Haliotis cracherodii cracherodii is also unusual as it has an ovate form, is imperforate, shows an exserted spire, and has prickly ribs.

A mantle cleft in the shell impresses a groove in the shell, in which are the row of holes characteristic of the genus. These holes are respiratory apertures for venting water from the gills and for releasing sperm and eggs into the water column. They make up what is known as the selenizone which forms as the shell grows. This series of eight to 38 holes is near the anterior margin. Only a small number is generally open. The older holes are gradually sealed up as the shell grows and new holes form. Each species has a typical number of open holes, between four and 10, in the selenizone. An abalone has no operculum. The aperture of the shell is very wide and nacreous.

The exterior of the shell is striated and dull. The color of the shell is very variable from species to species which may reflect the animal's diet.[5] The iridescent nacre that lines the inside of the shell varies in color from silvery white, to pink, red and green-red to deep blue, green to purple.

The animal has fimbriated head lobes and side lobes which are fimbriated and cirrated. The radula has small median teeth, and the lateral teeth are single and beam-like. They have about 70 uncini, with denticulated hooks, the first four very large. The rounded foot is very large in comparison to most molluscs. The soft body is coiled around the columellar muscle, and its insertion, instead of being on the columella, is on the middle of the inner wall of the shell. The gills are symmetrical and both well developed.[10]

These snails cling solidly with their broad, muscular foot to rocky surfaces at sublittoral depths, although some species such as Haliotis cracherodii used to be common in the intertidal zone. Abalones reach maturity at a relatively small size. Their fecundity is high and increases with their size, laying from 10,000 to 11 million eggs at a time. The spermatozoa are filiform and pointed at one end, and the anterior end is a rounded head.[11]

Distribution

The haliotid family has a worldwide distribution, along the coastal waters of every continent, except the Pacific coast of South America, the East Coast of the United States, the Arctic, and Antarctica.[12] The majority of abalone species are found in cold waters, such as off the coasts of New Zealand, South Africa, Australia, Western North America, and Japan.

Structure and properties of the shell

The shell of the abalone is exceptionally strong and is made of microscopic calcium carbonate tiles stacked like bricks. Between the layers of tiles is a clingy protein substance. When the abalone shell is struck, the tiles slide instead of shattering and the protein stretches to absorb the energy of the blow. Material scientists around the world are studying this tiled structure for insight into stronger ceramic products such as body armor.[13] The dust created by grinding and cutting abalone shell is dangerous; appropriate safeguards must be taken to protect people from inhaling these particles.[14]

Human use

The meat (foot muscle) of abalone is used for food, and the shells of abalone are used as decorative items and as a source of mother of pearl for jewelry, buttons, buckles, and inlay.[16] Abalone shells have been found in archaeological sites around the world, ranging from 100,000-year-old deposits at Blombos Cave in South Africa to historic Chinese abalone middens on California's Northern Channel Islands.[17][18] On the Channel Islands (California), where abalones were harvested by Native Americans for at least 12,000 years, the size of red abalone shells found in middens declines significantly after about 4000 years ago, probably due to human predation. Worldwide, abalone pearls have also been collected for centuries.

Farming

Farming of abalone began in the late 1950s and early 1960s in Japan and China.[19] Since the mid-1990s, there have been many increasingly successful endeavors to commercially farm abalone for the purpose of consumption.[20] Overfishing and poaching have reduced wild populations to such an extent that farmed abalone now supplies most of the abalone meat consumed. The principal abalone farming regions are China, Taiwan,[21] Japan, and Korea. Abalone is also farmed in Australia, Canada, Chile, France,[22]Iceland, Ireland, Mexico, Namibia, New Zealand, South Africa, Spain,[23] Thailand, and the United States.[24]

After trials in 2012,[25] a commercial "sea ranch" was set up in Flinders Bay, Western Australia to raise abalone. The ranch is based on an artificial reef made up of 5000 (As of April 2016) separate concrete units called abitats (abalone habitats). The 900 kilograms (2,000 lb) habitats can host 400 abalone each. The reef is seeded with young abalone from an onshore hatchery.

The abalone feed on seaweed that has grown naturally on the habitats; with the ecosystem enrichment of the bay also resulting in growing numbers of dhufish, pink snapper, wrasse, Samson fish among other species.

Brad Adams, from the company, has emphasised the similarity to wild abalone and the difference from shore-based aquaculture. "We're not aquaculture, we're ranching, because once they're in the water they look after themselves."[26][27]

Consumption

Abalones have long been a valuable food source for humans in every area of the world where a species is abundant. The meat of this mollusc is considered a delicacy in certain parts of Latin America (especially Chile), France, New Zealand, Southeast Asia, and East Asia (especially in China, Vietnam, Japan, and Korea). In Chinese-speaking regions, abalone is commonly known as bao yu, and sometimes forms part of a Chinese banquet. In the same way as shark fin soup or bird's nest soup, abalone is considered a luxury item, and is traditionally reserved for special occasions such as weddings and other celebrations. However, the availability of commercially farmed abalone has allowed more common consumption of this once rare delicacy.

As abalone became more popular and less common, the prices adjusted accordingly. In the 1920s, a restaurant-served portion of abalone, about 4 ounces, would cost (in inflation adjusted dollars) about $7; by 2004, the price had risen to $75.[28] In America, prior to this time, abalone was predominantly eaten, gathered, and prepared by Chinese immigrants.[29] Before that, abalone were collected to be eaten, and used for other purposes by Native American tribes.[30] By 1900, laws were passed in California to outlaw the taking of abalone above the intertidal zone. This forced the Chinese out of the market and the Japanese perfected diving, with or without gear, to enter the market. By the time of the exposition, Americans were starting to discover abalone. The popularity of abalone, along with many other fish and shellfish, increased as the exposition exhibited 365 varieties of fish with cooking demonstrations, and a 1300-seat dining hall.[31]

In Japan, live and raw abalones are used in awabi sushi, or served steamed, salted, boiled, chopped, or simmered in soy sauce. Salted, fermented abalone entrails are the main component of tottsuru, a local dish from Honshū. Tottsuru is mainly enjoyed with sake.[32]

In California, abalone meat can be found on pizza, sautéed with caramelized mango, or in steak form dusted with cracker meal and flour.[33]

Sport harvesting

Australia

Tasmania supplies about 25% of the yearly world abalone harvest.[34] Around 12,500 Tasmanians recreationally fish for blacklip and greenlip abalone. For blacklip abalone, the size limit varies between 138 mm (5.4 in) for the southern end of the state and 127 mm (5.0 in) for the northern end of the state.[35] Greenlip abalones have a minimum size of 145 mm (5.7 in), except for an area around Perkins Bay in the north of the state where the minimum size is 132 millimetres (5.2 in). With a recreational abalone licence, the bag limit is 10 per day, with a total possession limit of 20. Scuba diving for abalone is allowed, and has a rich history in Australia. (Scuba diving for abalone in the states of New South Wales and Western Australia is illegal; a free-diving catch limit of two is allowed).[36][37]

Victoria has had an active abalone fishery since the late 1950s. The state is sectioned into three fishing zones, Eastern, Central and Western, with each fisher required a zone-allocated licence. Harvesting is performed by divers using surface-supplied air "hookah" systems operating from runabout-style, outboard-powered boats. While the diver seeks out colonies of abalone amongst the reef beds, the deckhand operates the boat, known as working "live" and stays above where the diver is working. Bags of abalone pried from the rocks are brought to the surface by the diver or by way of "shot line", where the deckhand drops a weighted rope for the catch bag to be connected then retrieved. Divers measure each abalone before removing from the reef and the deckhand remeasures each abalone and removes excess weed growth from the shell. Since 2002, the Victorian industry has seen a significant decline in catches, with the total allowable catch reduced from 1440 to 787 tonnes for the 2011/12 fishing year, due to dwindling stocks and most notably the abalone virus ganglioneuritis, which is fast-spreading and lethal to abalone stocks.

United States

Two highly endangered white abalone: Prohibitions on commercial and recreational harvest of this species have been in place since 1996.

Sport harvesting of red abalone is permitted with a California fishing license and an abalone stamp card. In 2008, the abalone card also came with a set of 24 tags. This was reduced to 18 abalone per year in 2014, and as of 2017 the limit has been reduced to 12, only nine of which may be taken south of Mendocino County. Legal-size abalone must be tagged immediately.[38] Abalone may only be taken using breath-hold techniques or shorepicking; scuba diving for abalone is strictly prohibited.[39] Taking of abalone is not permitted south of the mouth of the San Francisco Bay.[40] A size minimum of 7 in (180 mm) measured across the shell is in place. A person may be in possession of only three abalone at any given time.[41][42]

As of 2017, Abalone season is May to October, excluding July. Transportation of abalone may only legally occur while the abalone is still attached in the shell. Sale of sport-obtained abalone is illegal, including the shell. Only red abalone may be taken, as black, white, pink, flat, green, and pinto abalone are protected by law.[41]

An abalone diver is normally equipped with a thick wetsuit, including a hood, bootees, and gloves, and usually also a mask, snorkel, weight belt, abalone iron, and abalone gauge. Alternatively, the rock picker can feel underneath rocks at low tides for abalone. Abalone are mostly taken in depths from a few inches up to 10 m (33 ft); less common are freedivers who can work deeper than 10 m (33 ft). Abalone are normally found on rocks near food sources such as kelp. An abalone iron is used to pry the abalone from the rock before it has time to fully clamp down. Divers dive from boats, kayaks, tube floats, or directly off the shore.[39]

The largest abalone recorded in California is 12.34 in (31.3 cm), caught by John Pepper somewhere off the coast of San Mateo County in September 1993.[43]

New Zealand

In New Zealand, abalone is called pāua (/ˈpaʊə/, from the Māori language). Haliotis iris (or blackfoot pāua) is the ubiquitous New Zealand pāua, the highly polished nacre of which is extremely popular as souvenirs with its striking blue, green, and purple iridescence. Haliotis australis and Haliotis virginea are also found in New Zealand waters, but are less popular than H. iris.

Like all New Zealand shellfish, recreational harvesting of pāua does not require a permit provided catch limits, size restrictions, and seasonal and local restrictions set by the Ministry for Primary Industries (MPI) are followed. The legal recreational daily limit is 10 per diver, with a minimum shell length of 125 mm (4.9 in) for H. iris and 80 mm (3.1 in) for H. australis. In addition, no person may be in possession, even on land, of more than 20 pāua or more than 2.5 kg (5.5 lb) of pāua meat at any one time. Pāua can only be caught by free-diving; it is illegal to catch them using scuba gear.

An extensive global black market exists in collecting and exporting abalone meat. This can be a particularly awkward problem where the right to harvest pāua can be granted legally under Māori customary rights. When such permits to harvest are abused, it is frequently difficult to police. The limit is strictly enforced by roving Ministry for Primary Industries fishery officers with the backing of the New Zealand Police. Poaching is a major industry in New Zealand with many thousands being taken illegally, often undersized. Convictions have resulted in seizure of diving gear, boats, and motor vehicles and fines and in rare cases, imprisonment.

South Africa

The largest abalone in South Africa, Haliotis midae, occurs along roughly two-thirds of the country’s coastline. Abalone-diving has been a recreational activity for many years, but stocks are currently being threatened by illegal commercial harvesting.[44] In South Africa, all persons harvesting this shellfish need permits that are issued annually, and no abalone may be harvested using scuba gear.

For the last few years, however, no permits have been issued for collecting abalone, but commercial harvesting still continues as does illegal collection by syndicates.[45]
In 2007, because of widespread poaching of abalone, the South African government listed abalone as an endangered species according to the CITES section III appendix, which requests member governments to monitor the trade in this species. This listing was removed from CITES in June 2010 by the South African government and South African abalone is no longer subject to CITES trade controls. Export permits are still required, however.
The abalone meat from South Africa is prohibited for sale in the country to help reduce poaching; however, much of the illegally harvested meat is sold in Asian countries. As of early 2008, the wholesale price for abalone meat was approximately US$40.00 per kilogram. There is an active trade in the shells, which sell for more than US$1,400 per metric tonne.

Channel-Islands, Brittany and Normandy

Ormers (Haliotis tuberculata) are considered a delicacy in the British Channel Islands as well as in adjacent areas of France, and are pursued with great alacrity by the locals. This, and a recent lethal bacterial disease,[46] has led to a dramatic depletion in numbers since the latter half of the 19th century, and "ormering" is now strictly regulated in order to preserve stocks. The gathering of ormers is now restricted to a number of 'ormering tides', from January 1 to April 30, which occur on the full or new moon and two days following. No ormers may be taken from the beach that are under 80 millimetres (3.1 in) in shell length. Gatherers are not allowed to wear wetsuits or even put their heads underwater. Any breach of these laws is a criminal offense and can lead to fine of up to £5,000 or six months in prison.[47] The demand for ormers is such that they led to the world's first underwater arrest, when Mr. Kempthorne-Leigh of Guernsey was arrested by a police officer in full diving gear when illegally diving for ormers.[48]

Decorative items

The highly iridescent inner nacre layer of the shell of abalone has traditionally been used as a decorative item, in jewelry,[5] buttons, and as inlay in furniture and in musical instruments such as on fret boards and binding of guitars, etc.[49]

Abalone pearl jewelry is very popular in New Zealand and Australia, in no minor part due to the marketing and farming efforts of pearl companies. Unlike the Oriental Natural, the Akoya pearl, and the South Sea and Tahitian cultured pearls, abalone pearls are not primarily judged by their roundness. The inner shell of the abalone is an iridescent swirl of intense colours, ranging from deep cobalt blue and peacock green to purples, creams and pinks. Therefore, each pearl, natural or cultured, will have its own unique collage of colours.

The shells of abalone are occasionally used in New Age smudging ceremonies to catch falling ash. They have also been used as incense burners.

Native use

Abalone has been an important staple in native cultures around the world, specifically in Africa and on the North American West coast. The meat was used as food, and the shell was used as currency for many tribes.[50]

Threat of extinction

Abalones have been identified as one of the many classes of organism threatened with extinction due to overfishing and the acidification of oceans from anthropogeniccarbon dioxide,[51] as reduced pH erodes their shells. It is predicted that abalones will become extinct in the wild within 200 years at current rates of carbon dioxide production. Currently the white, pink, and green abalone are on the federal endangered species list, and possible restoration sites have been proposed for the San Clemente Island and Santa Barbara Island areas.[52] The possibility of farming abalone to be reintroduced into the wild has also been proposed, with these abalone having special tags to help track the population.[53]

Species

The number of species that are recognized within the genus Haliotis has fluctuated over time, and depends on the source that is consulted. The number of recognized species range from 30[6] to 130.[7] This list finds a compromise using the "WoRMS database", plus some species that have been added, for a total of 57.[4][54] The majority of abalone have not been rated for conservation status. Those that have been reviewed tend to show that the abalone in general is an animal that is declining in numbers, and will need protection throughout the globe.

^Fitzgerald, Bridget (28 August 2014). "First wild abalone farm in Australia built on artificial reef". Australian Broadcasting Corporation Rural. Australian Broadcasting Corporation. Retrieved 23 April 2016. It's the same as the wild core product except we've got the aquaculture advantage which is consistency of supply.

Anon (2014). "Abalone Viral Ganglioneuritis". Department of Primary Industries, Parks, Water and Environment. Tasmanian Government. Archived from the original on 16 August 2014. Retrieved 16 August 2014.

Anon (2014a). "Abalone Fishing". Department of Primary Industries, Parks, Water and Environment. Tasmanian Government. Archived from the original on 16 August 2014. Retrieved 16 August 2014.

Anon (2014b). "Ormering Tides 2014". visitguernsey.com. State of Guernsey Commerce and Employment. Archived from the original on 17 August 2014. Retrieved 16 August 2014.

Dauphin, Y.; Cuif, J. P.; Mutvei, H.; Denis, A. (1989). "Mineralogy, Chemistry and Ultrastructure of the External Shell-layer in Ten Species of Haliotis With Reference to Haliotis tuberculata (Mollusca, Archaeogastropoda)". Bulletin of the Geological Institutions of the University of Uppsala. 15: 7–38. ISSN0302-2749.

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